1. Field of the Invention
The present invention relates to an optical system and a projection display apparatus using the same.
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 2001-154152 discloses a color splitting and combining optical system using a wavelength selective polarization rotor between a reflective liquid crystal display (“LCD”) element and a projection lens. However, the contrast lowers because the wavelength selective polarization rotor causes light in a polarization state different from a desired polarization state. Accordingly, JP 2006-071761 discloses an embodiment that does not arrange a wavelength selective polarization rotator between the LCD element and the projection lens utilizing, as a synthesizer of three colored light fluxes, an element that serves as a dichroic mirror for a certain wavelength range and to provide a polarization splitting and synthesizing characteristic for other wavelength ranges.
JP 2006-071761 arranges a wavelength selective polarizing plate that severs as a polarizing plate for a specific wavelength range between the LCD element and the projection lens, but the polarizing plate has a transmittance of about 80-90% and absorbs a large amount of light even in a transmitting axis direction. Due to the recent request for a higher brightness, the polarizing plate that absorbs a large amount of light causes to shorten the product life.